U.S. patent number 7,993,820 [Application Number 11/775,896] was granted by the patent office on 2011-08-09 for pattern manufacturing equipments, organic thin-film transistors and manufacturing methods for organic thin-film transistor.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Masahiko Ando, Shuji Imazeki, Tomohiro Inoue.
United States Patent |
7,993,820 |
Inoue , et al. |
August 9, 2011 |
Pattern manufacturing equipments, organic thin-film transistors and
manufacturing methods for organic thin-film transistor
Abstract
A liquid film applicator means can apply a photosensitive
lyophobic film 18 to a substrate 16. An exposure unit 10 is placed
on the back side of the substrate and forms the lyophobic film
applied on the substrate into a pattern in alignment with gate
electrodes 13. A dropping unit 55 drops a test liquid to a surface
of the substrate having a pattern of the lyophobic film formed by
the exposure means. A measuring means 58 detects the droplet
dropped by the dropping unit. A determining means determines
whether the pattern of the lyophobic film formed by the exposure
means is proper or not based on the droplet detected by the
detecting means.
Inventors: |
Inoue; Tomohiro (Tsukuba,
JP), Ando; Masahiko (Hitachinaka, JP),
Imazeki; Shuji (Hitachi, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
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Family
ID: |
38948346 |
Appl.
No.: |
11/775,896 |
Filed: |
July 11, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080012013 A1 |
Jan 17, 2008 |
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Foreign Application Priority Data
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Jul 11, 2006 [JP] |
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2006-189944 |
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Current U.S.
Class: |
430/325; 118/624;
118/211; 430/303; 347/19; 347/5; 430/5; 430/270.1; 438/907;
438/908; 438/909; 438/913; 430/9; 403/326; 430/302 |
Current CPC
Class: |
H01L
51/0012 (20130101); Y10S 438/907 (20130101); Y10S
438/908 (20130101); Y10T 403/60 (20150115); H01L
27/283 (20130101); Y10S 438/909 (20130101); Y10S
438/913 (20130101); H01L 51/0545 (20130101) |
Current International
Class: |
G03F
1/00 (20060101) |
Field of
Search: |
;430/9,302,303,325,326,5,270.1 ;438/913,907,909,759-794,270,908
;347/19,5 ;118/211,624 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2003121384 |
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Apr 2003 |
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JP |
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2004319897 |
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Nov 2004 |
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JP |
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2005079560 |
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Mar 2005 |
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JP |
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2005-11124 |
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Jan 2005 |
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KR |
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Other References
Korean Office Action dated Jun. 23, 2008. cited by other .
Office Action in Taiwan Patent Application 096119142, mailed Aug.
5, 2010, (pp. 1-6). cited by other.
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Primary Examiner: Gurley; Lynne A
Assistant Examiner: Gebreyesus; Yosef
Attorney, Agent or Firm: Antonelli, Terry, Stout &
Kraus, LLP.
Claims
The invention claimed is:
1. A pattern manufacturing equipment for manufacturing a pattern on
a transparent substrate having a pattern of a number of identical
gate electrodes formed regularly thereon, comprising: a lyophobic
film applicator means for applying a lyophobic film on the
transparent substrate; an exposure means placed on the back of the
transparent substrate for forming the lyophobic film applied on the
transparent substrate into a pattern in alignment with the pattern
of the gate electrodes; a liquid dropping means for dropping a test
liquid to form a first droplet of the test liquid on a surface of
the lyophobic film formed by the exposure means and to drop a
second droplet of the test liquid to a surface of the transparent
substrate where the lyophobic film has been removed; a measuring
means for detecting diameters of the first and second droplets
dropped by the liquid dropping means; and a determining means for
determining whether the lyophobic film has been properly formed by
the exposure means based on the diameter of the first droplet and
for determining whether the lyophobic film has been removed from
the surface of the transparent substrate by determining the
diameter of the second droplet.
2. The pattern manufacturing equipment according to claim 1,
further comprising an applicator means for exclusively applying a
source electrode and a drain electrode to portions without forming
the lyophobic film on the transparent substrate after formations of
the pattern of the lyophobic film by the exposure means.
Description
FIELD OF THE INVENTION
The present invention relates to a pattern manufacturing equipment
for manufacturing a pattern on a substrate, an organic thin-film
transistor and a manufacturing method for an organic thin-film
transistor.
BACKGROUND OF THE INVENTION
An exemplary method for manufacturing an organic thin-film
transistor in the related art has been described in
JP-A-2005-79560. In the described pattern manufacturing method for
providing a source electrode and a drain electrode in an organic
thin-film transistor with high accuracy, a substrate is covered
with a lyophobic film and a gate electrode is used as a mask to
apply ultraviolet (UV) radiation or radiated light to the back of
the gate electrode. The lyophobic film is thus vaporized and
removed except the area masked by the gate electrode to form a
pattern on the substrate. The source electrode and the drain
electrode are formed in the area where the lyophobic film was
removed.
JP-A-2004-319897 has disclosed a method in which a lyophobic film
is applied onto a substrate, a photomask formed in a predetermined
pattern is placed on the lyophobic film, and ultraviolet radiation
or electron beams are radiated to the lyophobic film. The lyophobic
film is decomposed, vaporized and removed by the ultraviolet
radiation or electron beams and then a lyophilic portion is formed
in the substrate to which the ultraviolet radiation or electron
beams are applied, except the portion covered with the
photomask.
On the other hand, an exemplary method for testing a wet pattern
formed on a surface of a substrate has been described in
JP-A-2003-121384. The described method includes forming a lyophobic
pattern having a little wettability of a liquid on a substrate and
a lyophilic pattern having high wettability of a liquid on the
substrate. Then, a test liquid is attached to the surface of the
lyophilic pattern, light is applied to the attached test liquid,
and the light reflected by the test liquid and the light
transmitted through the test liquid are analyzed to examine the
lyophilic area on the substrate surface, thereby detecting any
defect in the wet pattern.
BRIEF SUMMARY OF THE INVENTION
The pattern manufacturing method described in JP-A-2005-79560 is a
so-called SALSA (self alignment and self assembly) method in which
the gate electrode is used for the pattern manufacturing to
eliminate the need for a new positioning means, and thus high
accuracy is advantageously provided in positioning. The lyophobic
film in the area covered with the gate electrode is left even after
the ultraviolet radiation or the like is applied to the back
thereof, while the lyophobic film in the area exposed to the
ultraviolet radiation or the like is removed.
The lyophobic film, however, is transparent and thin, so that it is
not easy to make a distinction between the area where the lyophobic
film is left and the area where the lyophobic film was removed. In
addition, when a pattern manufacturing method similar to that
described in JP-A-2005-79560 was used, the present applicants found
that application of ultraviolet radiation or the like to the
lyophobic film for more than an appropriate time period or longer
caused a problem in which the lyophobic film was removed in the
area masked by a gate electrode due to diffraction of light or the
like.
In other words, the method described in JP-A-2005-79560 cannot
provide a predetermined pattern unless proper exposure time periods
according to various materials are used. However, the proper
exposure time periods have not been considered sufficiently in
JP-A-2005-79560. Thus, the use of a deteriorated material or a
faulty exposure apparatus may lead to the resulting wet pattern
different from a designed pattern.
JP-A-2004-319897 has an advantage that the substrate does not need
to be transparent since the photomask can be used to apply
ultraviolet radiation or electron beams from above the lyophobic
film similarly to JP-A-2005-79560. However, the method described in
JP-A-2004-319897 cannot provide a predetermined pattern unless a
proper exposure time is used. In addition, the pattern
manufacturing method requires a separate means for positioning.
In the method for testing a wet pattern described in
JP-A-2003-121384, the test liquid is attached only to the lyophilic
area and is observed. As a result, the pattern in the lyophilic
area can be examined, but it is difficult to detect the lyophobic
property or defect in the lyophobic film. If any defect is
overlooked and the subsequent steps are continued in the method,
those steps may be wasted in the end to reduce the yield in
substrate manufacturing. In addition, since the wettability is
examined after the lyophilic pattern and the lyophobic pattern are
formed, it is necessary to remove the wet pattern film and apply a
new film after any defect is detected.
The present invention has been made in view of the abovementioned
problems in the related art, and it is an object thereof to improve
the productivity of an organic thin-film transistor. It is another
object of the present invention to improve the reliability of an
organic thin-film transistor by manufacturing a stable wet pattern
on a substrate. It is still another object of the present invention
to test a pattern manufactured on a substrate easily and
reliably.
Other objects, features and advantages of the invention will become
apparent from the following description of the embodiments of the
invention taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing an example of a pattern
manufacturing equipment according to the present invention;
FIG. 2 is a flow chart explaining steps of manufacturing an organic
thin-film transistor according to the present invention;
FIGS. 3(a) to 3(f) are longitudinal sectional views showing an
organic thin-film transistor at the respective steps shown in FIG.
2;
FIG. 4 is a schematic diagram for explaining how to manufacture a
pattern on a substrate;
FIG. 5 is a flow chart explaining steps of manufacturing the
organic thin-film transistor according to the present
invention;
FIG. 6 is a graph for explaining a relationship between an exposure
time and a droplet diameter on a substrate;
FIGS. 7(a) and 7(b) are a longitudinal sectional view and a plan
view showing an example of the organic thin-film transistor
according to the present invention; and
FIG. 8 is a schematic diagram for explaining the position of
application of a test liquid.
DESCRIPTION OF REFERENCE NUMERALS
1 ORGANIC THIN-FILM TRANSISTOR 10 EXPOSURE UNIT 12 SEMICONDUCTOR
LAYER 13 GATE ELECTRODE 14 SOURCE ELECTRODE 15 DRAIN ELECTRODE 16
SUBSTRATE 17 GATE INSULATOR 55 DISPENSER (DROPPING UNIT) 114-117
DROPLET
DETAILED DESCRIPTION OF THE INVENTION
According to an aspect, the present invention provides a pattern
manufacturing equipment for manufacturing a pattern in a
transparent substrate having a pattern of a number of identical
gate electrodes formed regularly thereon, including a lyophobic
film applicator means for applying a lyophobic film to the
substrate, an exposure means placed on the back of the substrate
for forming the lyophobic film applied on the substrate into a
pattern in alignment with the pattern of the gate electrodes, a
liquid dropping means for dropping a test liquid to a surface of
the substrate having the pattern of the lyophobic film formed by
the exposure means, a measuring means for detecting a droplet
dropped by the liquid dropping means, and a determining means for
determining whether the pattern of the lyophobic film formed by the
exposure means is proper or not based on the droplet detected by
the detecting means.
It is desirable to include an applicator means for exclusively
applying a source electrode and a drain electrode to portions
without forming the lyophobic film on the substrate after
formations of the pattern of the lyophobic film by the exposure
means.
According to another aspect, the present invention provides an
organic thin-film transistor including a transparent substrate, a
gate electrode formed on a surface of the transparent substrate, a
gate insulator formed to cover the gate electrode and the
transparent substrate, a source electrode and a drain electrode
exclusively formed at a position on a surface of the gate
insulator, the position being not on the upper surface of the gate
electrode, and a semiconductor layer formed to connect a surface at
an end of the source electrode and a surface at an end of the drain
electrode to the surface of the gate insulator corresponding to the
gate electrode. The semiconductor layer is provided by forming a
pattern of a lyophobic film in alignment with the gate electrode on
the surface of the gate insulator and then by removing the
lyophobic film, and the pattern of the lyophobic film is formed to
have substantially the same width as the width of the gate
electrode.
According to yet another aspect, the present invention provides a
manufacturing method for an organic thin-film transistor, including
the steps of a gate electrode manufacturing step of manufacturing a
pattern of a number of identical gate electrodes regularly on a
transparent substrate, a gate insulator manufacturing step of
manufacturing a gate insulator on a surface of the gate electrode
and a surface of the substrate, a lyophilic/lyophobic pattern
manufacturing step of applying a lyophobic film to a surface of the
gate electrode and forming a pattern of the lyophobic film in
alignment with the pattern of the gate electrodes by light from the
exposure means provided on the back of the substrate, a
source/drain electrode manufacturing step of exclusively applying a
source electrode and a drain electrode to a portion of the pattern
of the lyophobic film in alignment with the gate electrode, the
portion having no lyophobic film, and a semiconductor layer
manufacturing step of removing the lyophobic film remaining on the
substrate and manufacturing a semiconductor layer connecting the
portion where the lyophobic film has been removed to the source
electrode and the drain electrode. The lyophilic/lyophobic pattern
manufacturing step includes dropping a test liquid to the surface
of the substrate during the formation of the pattern of the
lyophobic film by the exposure means, detecting a droplet of the
test liquid to determine the size thereof, and determining whether
the pattern of the lyophobic film formed by the exposure means is
proper or not based on the determined droplet diameter.
According to still another aspect, the present invention provides a
pattern manufacturing equipment including a lyophobic film
manufacturing means for forming a lyophobic film having wettability
on a surface of a transparent substrate, a removing means for
partially removing the lyophobic film from the surface of the
substrate, a droplet dropping means for dropping a test liquid to
the surface of the substrate from which the lyophobic film has been
partially removed, and a measuring means for detecting the diameter
of the dropped droplet.
It is preferable to include an electrode pattern manufacturing
means for forming a gate electrode on the substrate prior to the
formation of the lyophobic film on the substrate. It is desirable
that the droplet dropping means for dropping the test liquid
includes a control means for performing control such that the test
liquid is dropped to both of a lyophobic area where the lyophobic
film remains and a lyophilic area where the lyophobic film has been
removed.
The removing means preferably includes exposure means for applying
light energy to the substrate. It is preferable that the droplet
dropping means for dropping the test liquid is located on the front
side of the substrate, the exposure means is located on the back
side of the substrate, and the light energy is applied to the
lyophobic film applied on the substrate from the back side of the
substrate to partially remove the lyophobic film. The measuring
means is preferably located on the front side of the substrate. The
droplet dropping means and the measuring means may be movable
within an exposure range of the exposure means.
According to the present invention, the test liquid is continuously
observed from above the substrate during the removal of the
lyophobic film applied on the substrate in the pattern
manufacturing step in which the lyophobic film is removed, so that
the productivity of the organic thin-film transistor is improved.
The stable wet pattern is formed on the substrate to enhance the
reliability of the organic thin-film transistor. In addition, since
the test liquid is detected from above the substrate, the pattern
formed on the substrate can be tested easily and reliably.
Examples of a pattern manufacturing equipment and a pattern
manufacturing method according to the present invention will
hereinafter be described with reference to the accompanying
drawings. FIGS. 7(a) and 7(b) show an example of an organic
thin-film transistor (TFT) manufactured by a pattern manufacturing
equipment according to the present invention. FIG. 7(a) is a
longitudinal sectional view and FIG. 7(b) is a top view. An organic
thin-film transistor 1 includes a transparent substrate 16, a gate
electrode 13 placed thereon, and a gate insulator 17 covering an
upper surface of the substrate 16 including the gate electrode 13
thereon.
A semiconductor layer 12 is provided on an upper surface of the
gate insulator 17 and a position corresponding to above the gate
electrode 13. A drain electrode 15 and a source electrode 14 are
exclusively provided on the upper surface of the gate insulator 17
except the area where the semiconductor layer 12 is provided. A
portion of the drain electrode 15 and a portion of the source
electrode 14 are covered with the semiconductor layer 12. The
bottom surface of the single organic thin-film transistor 1
typically has a length of 0.1 to 0.3 mm in the horizontal direction
and a length of 0.1 to 0.3 mm in the vertical direction in FIG.
7(b). The gate electrode 13 has a width of approximately 5 to 50
.mu.m. The gate electrode 13 has a thickness of 400 nm, the gate
insulator 17 has a thickness of 300 nm, and each of the drain
electrode 15, the source electrode 14 and the semiconductor layer
12 has a thickness of approximately 0.1 .mu.m.
FIG. 2 is a flow chart showing the manufacturing process in an
example of the organic thin-film transistor 1 according to the
present invention. FIGS. 3(a) to 3(f) are longitudinal sectional
views showing the organic thin-film transistor 1 at the respective
steps shown in FIG. 2. The manufacturing process of the organic
thin-film transistor 1 is broadly classified into a gate electrode
manufacturing step 100, a gate insulator manufacturing step 110, a
lyophilic/lyophobic pattern manufacturing step 120, a source
electrode/drain electrode manufacturing step 130 and a
semiconductor layer manufacturing step 140 which are performed in
order. The details of each of the manufacturing steps will
hereinafter be described.
[Gate Electrode Manufacturing Step 100]
FIG. 3(a) is a longitudinal sectional view showing a substrate 160
provided by performing the gate electrode manufacturing step 100.
The substrate 160 has a size of 150 mm in a feed direction and 150
mm in a width direction in order to manufacture 300 organic
thin-film transistors each in the feed direction and the width
direction of the substrate 160. The substrate 160 includes an
insulating substrate 16 made of transparent material such as quartz
glass in the lowest layer. Gate electrodes 13 having a
predetermined pattern are formed regularly in the feed direction
and the width direction on an upper surface of the insulating
substrate 16. In the following description, the surface of the
insulating substrate 16 having the gate electrodes 13 formed
thereon is referred to as a front side and the surface opposite
thereto is referred to as a back side. The gate electrodes 13 are
made of chromium thin film having a thickness of 300 nm and are
formed by depositing chromium on the front side of the insulating
substrate 16 through sputtering and then patterning the chromium as
desired through photolithography.
[Gate Insulator Manufacturing Step 110]
FIG. 3(b) is a longitudinal sectional view showing a substrate 170
provided by performing the gate insulator manufacturing step 110
for manufacturing the gate insulator 17 on the substrate 160
manufactured at the gate electrode manufacturing step 110. Oxide
silicon is deposited through CVD on the front sides of the
substrate 160 and the gate electrode 13 to form the gate insulator
17. The gate insulator 17 has a thickness of 300 nm.
[Lyophilic/Lyophobic Pattern Manufacturing Step 120]
FIG. 3(c) is a longitudinal sectional view showing a substrate 180
at an immediate substep in the lyophilic/lyophobic manufacturing
step 120 for forming a lyophilic pattern and a lyophobic pattern on
the front side of the substrate 170 having the gate insulator 17
deposited thereon. FIG. 3(d) is a longitudinal sectional view
showing a substrate 190 provided after the lyophilic/lyophobic
manufacturing step is performed.
A photosensitive lyophobic film 18 is formed on the surface of the
gate insulator 17 formed in the substrate 170 to provide the
substrate 180. The photosensitive lyophobic film 18 is formed by
applying a solution containing lyophobic unimolecules dispersed in
a fluoride solvent before drying. The lyophobic unimolecules
dispersed in the fluoride solvent are an alkyl fluoride silane
coupling agent including a carbon chain, at least part of the chain
being terminated at a fluoride group, such as
CF.sub.3(CF.sub.2).sub.7(CH).sub.2SiCl.sub.3. In the example, it
was found that the contact angle of water on the photosensitive
lyophobic film 18 was 100 to 120 degrees and the manufactured
photosensitive lyophobic film 18 represented a desired lyophobic
property.
Exposure of the photosensitive lyophobic film 18 to ultraviolet
radiation causes decomposition and vaporization to remove the
photosensitive lyophobic film 18. The gate insulator 17 is exposed
in the portion where the photosensitive lyophobic film 18 was
removed. Thus, the ultraviolet radiation is applied to the back
side of the substrate 180 to form an exposed area where the
photosensitive lyophobic film 18 was removed and a non-exposed area
where the ultraviolet radiation is shielded by the gate electrode
13 to leave a photosensitive lyophobic film 18. In this manner, the
photosensitive lyophobic film 18 having substantially the same
pattern as that of the gate electrode 13 is provided. This results
in the substrate 190 having the lyophilic pattern and the lyophobic
pattern with different wettability. It was found that the contact
angle of water on the gate insulator 17 was 20 degrees or less, and
thus a desired lyophilic property was achieved in the substrate
190.
The gate electrode 13 is used as a mask to form the pattern of the
lyophobic film 18 similar to the pattern of the gate electrode 13
in the substrate 190. However, it is difficult to determine whether
the pattern of the lyophobic film 18 is substantially the same as
the patter of the gate electrode 13 since the lyophobic film 18 is
thin and transparent, and the underlying gate insulator 17 is also
transparent. In addition, even when they appear to be identical, a
portion of the pattern of the lyophobic film 18 may be narrower
than a predetermined width or may be broken on the way. Thus, it is
necessary to examine whether the lyophobic film 18 has the
predetermined pattern.
FIG. 6 shows how the photosensitive lyophobic film 18 applied onto
the gate insulator 17 is changed with an exposure time in a
relationship between an exposure time T and a droplet diameter d
when a fixed amount of droplet, a droplet of water in this case, is
dropped. This is the result of dropping the droplet to a portion
where the gate electrode 13 is not formed and the photosensitive
lyophobic film 18 is applied. A solid line 300 represents the
relationship between the exposure time T and the droplet diameter d
when exposure is performed at a predetermined intensity. With the
exposure time T, the droplet becomes more wettable (lyophilic) to
increase the droplet diameter d. After the elapse of a sufficient
exposure time, the photosensitive lyophobic film 18 is removed and
the droplet diameter is substantially constant.
The intensity of the ultraviolet radiation applied to the
photosensitive lyophobic film 18 depends on the states of the
substrate 16 and the gate insulator 17. To check the appropriate
progress of the acquisition of the lyophilic property in a
predetermined time period, the droplets are dropped from above the
substrate 180 during the manufacturing of the pattern of the
lyophobic film 18 through the ultraviolet radiation. The diameters
of the dropped droplets are measured successively. A pattern
manufacturing equipment capable of the measurement of droplet
diameters will hereinafter be described with reference to FIGS. 1
and 4.
FIGS. 1 and 4 are schematic diagrams showing the main portions of
the pattern manufacturing equipment. A pattern manufacturing
equipment 80 is used in patterning (FIG. 1) for manufacturing a
lyophilic pattern and a lyophobic pattern by removing part of the
photosensitive lyophobic film 18 and in test (FIG. 4) for testing
the deposition of the photosensitive lyophobic film 18.
The pattern manufacturing equipment 80 includes an exposure unit 10
with a low-pressure mercury vapor lamp below the substrate 180 or
190 in order to apply the ultraviolet radiation to the back side of
the substrate 180 or 190. A pair of feed rollers 59 is placed at a
position not interfering with the exposure unit 10 for putting the
substrate 180 or 190 thereon, introducing the substrate 180 or 190
into the pattern manufacturing equipment 80, and transferring the
substrate 180 or 190 to the facility for the next step. A dropping
unit 55 drops droplets 114 to 117 for test to predetermined
positions in accordance with the pattern of the gate electrode 13
on the substrate 180 or 190 fed by the feed rollers 59. A measuring
means 58 measures the diameters of the droplets 114 to 117 for
test.
To avoid interference of the manufacturing and the measurement of
the organic thin-film transistor 1, a dummy organic thin-film
transistor portion is formed on the periphery of the area where the
organic thin-film transistor is formed instead of the direct
measurement of the area of the substrate 180 or 190 where the
organic thin-film transistor 1 is manufactured. The dummy organic
thin-film transistor portion is used as a target of test of the
photosensitive lyophobic film 18 in this example. The dummy organic
thin-film transistor portion has dummy gate electrodes 13 in
substantially the same pattern as that in the regular organic
thin-film transistor 1. The ultraviolet radiation is also applied
to the back of the dummy organic thin-film transistor portion.
The measuring means 58 includes a CCD camera which manipulates
images of the droplets 114 to 117. The images are subjected to
image processing to determine the droplet diameter D. Since the
droplet diameter D relates to the wettability of the surface of the
substrate 180 and 190, the wettability is evaluated on the basis of
the previously calibrated relationship between the droplet diameter
D and the wet angle. The CCD camera is movable so that it can take
images of the droplets 114 to 117 dropped at arbitrary positions on
the substrate 180 or 190. Thus, the CCD camera may be retracted
from the exposure section other than when images are taken.
The test liquid dropping unit 55 may be formed of an apparatus
which can drop a fixed amount of test liquid such as a dispenser
and an inkjet. A dispenser is used in the example. The test liquid
dropping unit 55 is movable so that it can drop the test liquid at
arbitrary positions on the substrate 180 or 190 similarly to the
CCD camera. The test liquid droplets 114 to 117 are preferably
formed of a material having a lyophobic property of a contact angle
of approximately 90 degrees or more for the photosensitive
lyophobic film 18 and a lyophilic property of a contact angle of
approximately 20 degrees or less for the gate insulator 17. In the
example, the droplets 114 to 117 are realized by water produced
with an ion-exchange resin.
The test liquid is dropped to the dummy organic thin-film
transistor portion as descried above, thereby eliminating the need
for the subsequent steps of cleaning and removing the test liquid.
The feed rollers 59 are driven to feed the substrate 180 before
exposure to the position where the exposure unit 10 performs
exposure operation, wherein the substrate 180 is covered with the
photosensitive lyophobic film 18. The feed rollers 59 also feed the
substrate 190 to the next step after the exposure operation and the
wettability evaluation with the test liquid are finished.
The detailed operation procedure in the pattern manufacturing
equipment 80 will be described with reference to FIG. 5. Firstly,
description will be made for the operation in a test for checking
whether a proper film is used as the photosensitive lyophobic film
18. At a test liquid dropping step 200, the test liquid is dropped
to the surface of the substrate 180 by the dispenser 55. A control
means (which is not shown in the figure) performs control such that
the droplet 114 is dropped to a non-exposure area masked by the
previously formed dummy gate electrode 13a and the droplet 115 is
dropped to an exposure area where the dummy gate electrode 13a is
not formed. At a droplet diameter measuring step 210, the images of
the droplets 114 and 115 on the substrate 180 are taken by the CCD
camera and subjected to image processing by an image processing
means (which is not shown in the figure) to determine the diameters
of the droplets 114 and 115. The droplets 114 and 115 are dropped
at a plurality of different positions (five or more different
positions) to determine the average value and the standard
deviation of the diameters through the image processing.
At a step 220, it is determined whether or not the average diameter
and the standard deviation of the diameters of the droplets 114 and
115 are equal to predetermined values. If the average diameter of
the droplets is equal to or higher than the predetermined value or
if the standard deviation of the droplet diameters is equal to or
higher than the predetermined value, the dropping position is
changed and the flow returns to the dropping step 200 for dropping
the test liquid again. If the steps are repeated several times
(three times in the example) and the droplet diameters are still
larger than the predetermined value and thus it is determined that
the photosensitive lyophobic film 18 does not have a predetermined
lyophobic property (step 280), it is determined that an error
occurred at the previous step 100 or 110 shown in FIGS. 3(a) and
3(b) or in the manufacturing of the photosensitive lyophobic film
18, and the procedure is stopped at this point or the processing
conditions are changed at those steps.
If it is determined that the photosensitive lyophobic film 18 has
the predetermined lyophobic property, the flow moves to patterning
operation. The exposure unit 10 performs exposure on the substrate
180 from the back side thereof to form the lyophilic pattern and
the lyophobic pattern. After a predetermined time period has
elapsed since the start of the exposure, the flow moves to a test
liquid dropping step 230. As in the abovementioned test, the test
is performed in the dummy organic thin-film transistor portion
formed in the peripheral potion of the substrate. The droplet 116
is dropped to the non-exposure area formed by using the dummy gate
electrode 13a as a mask, and the droplet 117 is dropped to the
exposure area where the ultraviolet radiation is performed.
The diameters of the dropped droplets 116 and 117 are measured at a
droplet diameter measuring step 240. Since the photosensitive
lyophobic film 18 used in the example acquires the lyophilic
property after the ultraviolet radiation for approximately six
minutes, the test liquid is dropped at intervals of 15 seconds
after the start of the exposure. The diameters of the dropped
droplets 116 and 117 are measured by the CCD camera (step 240). It
is determined from the measured diameters of the droplets 116 and
117 whether the droplets 116 and 117 extend to a predetermined
droplet diameter, that is, whether the photosensitive lyophobic
film 18 is removed in a predetermined area of the substrate 180
through the exposure (step 250).
At the test steps from steps 230 to 250, the substrate 180 may be
stopped temporarily in the exposure of the ultraviolet radiation,
but the test operation is performed in parallel with the exposure
processing to improve the processing efficiency at the step 120 for
manufacturing the lyophilic pattern and the lyophobic pattern. At
the droplet diameter measuring step 240, the images of the droplets
116 and 117 are taken by the CCD camera as described above, and
then the droplet diameter d is calculated by a processing means
(which is not shown in the figure). At the step 250, if the droplet
diameter d of the droplet 117 is equal to or lower than a target
value do, the exposure is continued since it is not sufficient. The
dispenser 55 is moved to change the drop position of the test
liquid at the step 260, and then the flow returns to the step 230
to drop the test liquid again to a different position.
The test liquid drop position moving step 260 will be described in
more detail with reference to FIG. 8. In the example, the exposure
is performed while the substrate 180 is fed at a predetermined
rate. Instead of the exposure of the overall substrate 180, a
portion of the substrate 180 having a predetermined width in the
feed direction is exposed. Thus, in FIG. 8, a portion on the right
has been exposed for a longer time period, while a portion on the
left has been exposed for a shorter time period. In this case, if
the droplet diameter of the test liquid is measured at the same
position in the feed direction (position in the horizontal
direction), the test when the exposure time is substantially the
same time period can only be carried out.
Thus, the CCD camera is moved to the position in the feed direction
where the previously tested position 17a reaches after the elapse
of a time interval .DELTA.T (15 seconds). However, the position in
parallel with the position 17a corresponds to the previously
measured position 17b, so that the droplet of the previous test
liquid may affect the test. For this reason, a new measurement
position 17c is set to a position a predetermined distance away
from the position 17b in the vertical direction.
When the substrate 180 is stopped to exposure the ultraviolet
radiation, the exposure time is uniform over the exposure areas
corresponding to almost all areas of substrate 180. For this
reason, the test liquid may be dropped anywhere. If the measured
diameter d of the droplet 117 dropped in the exposure area extends
to the target value do shown in the graph of FIG. 6, it is
determined that the photosensitive lyophobic film 18 has the
lyophilic property. Although omitted in FIG. 5, the steps 230 to
250 are repeated in order to test all of the test areas set on the
substrate 180. After the test of all of the test areas, it is
determined that the pattern has been formed. While only the droplet
117 in the lyophilic area is evaluated in the above description,
the diameter of the droplet 116 in the lyophobic area is desirably
evaluated. According to the example, the wettability changed with
the exposure can be appropriately examined to form the lyophilic
pattern and lyophobic pattern stably.
[Source/Drain Electrode Manufacturing Step 130]
After it is checked that the substrate 190 is provided by forming
the pattern on the surface of the substrate 180, the drain
electrode 15 and the source electrode 14 are exclusively formed in
the lyophilic portion of the substrate 190. FIG. 3(e) is a
longitudinal sectional view showing a substrate 200 including the
drain electrode 15 and the source electrode 14 formed thereon. The
drain electrode 15 and the source electrode 14 are formed by
applying a conductive ink in a liquid state to the surface of the
substrate 190 from which the photosensitive lyophobic film 18 was
removed and then by fixing the conductive ink to the surface of the
substrate 190 through calcination at approximately 200 degrees.
The conductive ink is realized by a liquid mainly containing at
least one of metal particles, a metal complex, and a conductive
polymer and showing a sufficiently low resistance value after the
calcination. Specifically, it is possible to use a solution
containing metal particles having a diameter of approximately 10
.mu.m or less and mainly made of Au, Ag, Pd, pt, Cu, or Ni, or a
metal complex dispersed in a solvent such as water, toluene, and
xylene. It is also possible to use a solution such as PEDOT
(poly(3,4-ethylene dioxythiophene)), polyannin, and polypyrrole
provided by doping PSS (polystyrene sulfonate acid) which is a
conductive polymer.
In the example, a liquid (metal ink) containing Ag dispersed in a
solvent mainly made of water was used as the conductive ink. The
conductive ink extends on the surface of the gate insulator 17 due
to the lyophilic property, and is repelled by the photosensitive
lyophobic film 18 which is lyophobic. The drain electrode 15 and
the source electrode 14 are formed only in the lyophilic area in
alignment with the gate electrode 13. When applying the conductive
ink, it is preferable to use printing capable of application of a
solution with a dispenser, an inkjet, or a spray. In the example, a
dispenser capable of releasing a liquid by controlling pressure of
a nozzle is used.
[Semiconductor Layer Manufacturing Step 210]
FIG. 3(f) is a longitudinal sectional view showing a substrate 210
provided by forming the semiconductor layer 12 in the remaining
photosensitive lyophobic film 18 after it is checked that the drain
electrode 15 and the source electrode 14 are formed in the
substrate 200. At the semiconductor layer manufacturing step 140
shown in FIG. 2, the photosensitive lyophobic film 18 remaining at
the position corresponding to the gate electrode 13 is removed by a
low-pressure mercury lamp (which is not shown in the figure) which
is placed on the front side of the substrate 200. Next, the
semiconductor layer 12 is formed to cover a portion of the source
electrode 14 and a portion of the drain electrode 15 mainly in the
substrate surface 200 from which the photosensitive lyophobic film
18 was removed.
The semiconductor layer 12 is made of a material such as a
conjugate polymer compound such as polyphenylenevinylene and
polythiophene and an aromatic compound including a polyacene
compound such as antracene, tetracene, and pentacene. In the
example, a solution containing pentacene dissolved in a solvent
such as toluene and trichlorobenzene was used. For applying the
semiconductor layer 12 to the gate insulator 17, it is preferable
to use printing capable of application of a solution with a
dispenser, an inkjet, or a spray. In the example, a dispenser is
used similarly to the source/drain electrode manufacturing step
130. In the application operation, the semiconductor solution is
heated to approximately 150 to 200 degrees to maintain the
solubility of the semiconductor material. After the semiconductor
layer 12 is formed on the gate insulator 17, the organic thin-film
transistor 1 of a bottom gate type is provided in the substrate
210.
While the rectangular glass substrate is used as the substrate in
the example, a transparent film such as a plastic film may be used
for the material of the substrate. In this case, it is also
necessary to form a gate electrode not transparent in the
substrate.
It should be further understood by those skilled in the art that
although the foregoing description has been made on embodiments of
the invention, the invention is not limited thereto and various
changes and modifications may be made without departing from the
spirit of the invention and the scope of the appended claims.
* * * * *